Feminizing adrenal tumor identified by plasma steroid profiling.

Feminizing estrogen-secreting adrenocortical carcinomas (ACCs) are a rare, but an important differential diagnosis in men with rapidly developing gynecomastia. Biochemical evaluation is essential for a prompt diagnosis. Steroid hormone profiling using liquid chromatography mass spectrometry technology has the potential to improve early diagnosis of feminizing estrogen-secreting ACC.